Thin film solar cell technology is a subject of intense research since it holds the promise of high performance, combined with low cost. The chalcopyrite compound semiconductor CuInSe2 has shown its importance in optoelectronic devices mainly due to the excellent absorption characteristics of this material. However, since the energy gap of this compound (Eg = 1.0 eV) is slightly below the range required for optimum conversion efficiency, which is 1.2 to 1.5 eV for such devices, it is desirable to increase it a little in order to improve the device performance. This can be done by mixing this material with the compound CuGaSe2 (Eg = 1.7 eV) which leads to an available energy gap range between 1.0 and 1.7 eV for the system CuInxGa1-xSe2. CuInxGa1-xSe2 (CIGS) is direct band gap semiconductor with a large absorption coefficient. But thin film photovoltaic technologies comprising CuInS2 (CIS), CuInGaSe2 (CIGS) and CdTe rely on elements that are costly and rare in the earthâ€™s crust (e.g. In, Ga, Te) and are toxic (e.g. Cd). Hence, cost reduction and increased production, using abundantly available non-toxic elements, seem to be the main issues. Cu2ZnSnS4 (CZTS) and perovskite based solar cell, is one of the most promising candidates for low cost thin film solar cells, because of its suitable direct band gap between 1.4 and 1.5 eV and large absorption coefficient. Also it is composed of earth abundant and non-toxic elements, promising price reductions in future. Recently, research in this area has gained momentum due to the desirability of producing Ga, In and Cd free absorber layers and the potential to obtain new insights. I will present a brief overview of this topic.